Dinitroaniline Herbicide Phytotoxicity as Influenced by Soil Moisture and Herbicide Vaporization

Abstract

Effects of soil water and herbicide vapors on the phytotoxicity of eight dinitroaniline herbicides to oats (Avena sativa L. ‘Dal’) were studied. Oat primary root length was inhibited more by the herbicides than was shoot length or shoot fresh weight. All of the herbicides, except oryzalin (3,5-dinitro-N 4,N 4-dipropylsulfanilamide), inhibited primary root length through vapor activity. Vapors of dinitramine (N 4,N 4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) were most inhibitory. Herbicide vapor inhibition increased with temperature. Soil water affected oryzalin activity more than it did that of the other herbicides. Oryzalin phytotoxicity to the oat primary root was reduced more at the low soil water than was that of the other herbicides. Its low vapor activity apparently reduced its effectiveness in dry soil. Difference in magnitude of herbicide phytotoxicity between two soil moisture levels generally was more pronounced at lower herbicide concentration.